cmd/link: directly get max pc value in findfunctab

Change-Id: I70afd2f7b6783926174c4e66565b711cffeb97c5
Reviewed-on: https://go-review.googlesource.com/c/150141
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/link/internal/ld/pcln.go

@@ -520,10 +520,8 @@ func (ctxt *Link) findfunctab() {
 
 	// find min and max address
 	min := ctxt.Textp[0].Value
-	max := int64(0)
-	for _, s := range ctxt.Textp {
-		max = s.Value + s.Size
-	}
+	lastp := ctxt.Textp[len(ctxt.Textp)-1]
+	max := lastp.Value + lastp.Size
 
 	// for each subbucket, compute the minimum of all symbol indexes
 	// that map to that subbucket.